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ESR-lyoluminescence correlation studies of tris(hydroxymethyl)aminomethane
ESR-Lyoluminescence Correlation Studies of Tris(hydroxymethyl)aminomethane J. AZORIN and A. GUTi&REZ Department of Nuclear Physics Instituto National de Investigaciones Nucleares Salazar 52045, Mexico
This paper presents the ESR and LL dosimetric characteristics of tris(hydroxymethyl)aminomethane irradiated with QCo gamma radiation and compares them with those of mannose. Correlation of dose measurements by means of ESR and LL using tris showed agreement within 5% in the dose range from 20 to 3x1@ Gy.
KEYWORDS:
ESR; lyoluminescence;
free radicals; dosimetry.
INTRODUCTION
Lyoluminescence, the phenomenon of light emission accompanying the dissolution of irradiated solids in certain solvents, has been studied by a number of workers for use in dosimetry applications (Puite and Ettinger, 1982). The most widely used lyoluminescent materials for high dose dosimetry have been saccharides and amino acids (Ettinger and Puite, 1982). Various authors (Bartlett and Brown, 1979; Bartlett et al., 1982) have studied free radicals produced in saccharides, by electron spin resonance (ESR). Lyoluminescence (LL) properties of tris(hydroxymethyl)aminomethane, commonly referred as tris, were previously compared them with LL and ESR of mannose and sucrose (Azorin ef al., 1986). A LL dosimetry system to measure high radiation doses based on tris has also been reported (Azorin and Gutierrez, 1991). This paper presents a study of the dosimetric characteristics of tris obtained by means of ESR and LL techniques, and compares them with those of mannose.
EXPERIMENTAL
Samples (100 mg) of tris, (HOCH&CNH, (Sigma), and D,+,mannose (Merck), were irradiated under electronic equilibrium conditions in a Gammacell 200 @‘Counit at a dose rate of 2 kGy h-‘. ESR spectral measurements were carried out with a Varian X-band ESR spectrometer, employing 9 GHz phase sensitive detection at a constant microwave power level (20 dB) and at room temperature. Weighed amounts of gamma-irradiated tris and mannose (particle size 180-250 pm) in quartz sample tubes were placed in the ESR cavity. The spectra were obtained by scanning the magnetic field and registering them on an x-y recorder. Lyoluminescence readings were made in a thermoluminescence (TL) analyzer, modified to be used as LL reader, which was described earlier (Azorln et al., 1989). A solution 7x10“ mol ml“ of luminol in distilled water was used as the solvent. In each run, aliquots of 10 mg of irradiated sample were dissolved in 5&0.5 ml of solution injected during 10 s. Integration of emitted light photons was continued for 15 s so as to match with the optimum emission of the short-lived component of the LL decay curve after complete dissolution. Single crystals of tris were grown by slow evaporation of saturated aqueous solutions in order to identify the free radical species produced by irradiation of tris. 341
ESR dosimetry and applications
342
The crystals were irradiated at room temperature at an absorbed dose of 30 kGy and the ESR measurements made at room temperature.
RESULTS AND DISCUSSION Figure 1 shows the ESR spectra of gamma-irradiated tris and mannose. Each signal consists of several peaks due to the hyperfine interactions of unpaired electrons with the N and H atoms.
IA 315
Fig. 1. Firstderivative scale is in mT.
320
325
315
320
325
ESR spectrum of tris and mannose irradiated with “Co gamma radiation.
The
For the tris and mannose spectra, the areas (obtained from the double integral of the ESR spectrum) were plotted as a function of dose and compared with the LL response (Fig. 2). The ESR response of tris and mannose are fit to straight lines in logarithmic scale in the ranges from 5 to 10’ Gy for both. Saturation was reached at 3 x 104 Gy. The minimum measurable ESR dose for tris and mannose were 50 and 200 mGy, respectively. No ESR signal fading was observed up to 60 days storage at room temperature. The LL output of tris increases linearly from 5 to 107Gy, saturates, then slowly decreases (Fig. 2a). For mannose, the LL output increases linearly over the range from 3 to ICYGy, as was reported earlier (Azorfn et al., 1989). The LL threshold detection of gamma radiation for tris and mannose are 100 mGy and 500 mGy respectively. No fading was detected in tris and mannose for a period of 6 months after irradiation, when stored at room temperature.
100
’ .
40'
10' Ilose
Fig. 2. ESR and LL responses with gCo gamma radiation.
103
104
10'
‘*11’,’
a ’ lllm’
lo2
’
m“‘ti
103
Dose (GY 1 as a function of dose for: (a) tris and (b) marmose irradiated
104
343
ESR dosimetry and applications
ESR spectra of single-crystals of tris immediately after irradiation indicated the presence of more than one radical species signified by several overlapping lines along equivalent directions. Correlation of evaluated absorbed dose by means of ESR and LL measurements on simultaneously irradiated samples of tris and mannose revealed dose agreement within 5% in the ranges from 20 to 3x10* Gy, and from 50 to 10’ Gy for tris and mannose, respectively. Table 1 summarizes the ESR and LL characteristics of tris compared with dose of mannose.
Table 1. ESR and lyoluminescence characteristics of tris and mannose.
Characteristic ESR dose range (Gy) LL dose range (Gy) ESR detection threshold (mGy) LL detection threshold (mGy) ESR-fading (6 months) LL-fading (6 months)
I
I I I I
tris
mannose
s- 104
5 - 104
s- 103
50 100 nil nil
I
I I I I
3 - 103 200 500
nil nil
In summary, ESR measurements with tris allow determination of absorbed doses in the range of 5 to 104 Gy with an uncertainty of 3%. LL dose measurements in the range of 5 to 1oZGy can be determined with the same uncertainty. Correlation of dose measurements by means of ESR and LL using tris showed agreement within 5%. Thus, tris can be applied to both ESR and LL dosimetry.
REFERENCES Azorfn J., Gutierrez A. and Guadarrama L. (1986) Lyoluminescence of tris (hydroxymethyl) aminomethane in gamma dosimetry. Radiat. Prof. Dosim. 17, 423. Azorln J., Gutierrez A., Mufioz E. and Gleason R. (1989) Correlation of ESR with lyoluminescence dosimetry using some sugars. Appl. Radiat. Isot. 40, 87 1. Azorln J., Gutierrez A. (1991) Development of a lyoluminescence dosimetry system to measure high radiation doses. Proc. Int. Symp. on High Dose Dosimetryfor RadiationProcessing IAEA-SM-3 14 pp. 65-71. Bartlett D.T. and Brown J.K. (1979) Irradiation effects in D-mannose as studied by electron spin resonance spectroscopy. Radiat. En 41, 43. Bartlett D.T., Brown J.K. and Durrani S.A. (1982) Lyoluminescence and electron spin resonance measurements on D-mannose: effects of storage and annealing. Radiat. Efl 66, 233. Ettinger K.V. and Puite K.J. (1982) Lyoluminescence Dosimetry Part I. Principles. Appl. Radiat. Isot. 33, 1115. Puite K.J. and Ettinger K.V. (1982) Lyoluminescence Dosimetry Part II. State-of-the-Art. Appl. Radiat. Isot. 33, 1139.
This paper presents the ESR and LL dosimetric characteristics of tris(hydroxymethyl)aminomethane irradiated with QCo gamma radiation and compares them with those of mannose. Correlation of dose measurements by means of ESR and LL using tris showed agreement within 5% in the dose range from 20 to 3x1@ Gy.
KEYWORDS:
ESR; lyoluminescence;
free radicals; dosimetry.
INTRODUCTION
Lyoluminescence, the phenomenon of light emission accompanying the dissolution of irradiated solids in certain solvents, has been studied by a number of workers for use in dosimetry applications (Puite and Ettinger, 1982). The most widely used lyoluminescent materials for high dose dosimetry have been saccharides and amino acids (Ettinger and Puite, 1982). Various authors (Bartlett and Brown, 1979; Bartlett et al., 1982) have studied free radicals produced in saccharides, by electron spin resonance (ESR). Lyoluminescence (LL) properties of tris(hydroxymethyl)aminomethane, commonly referred as tris, were previously compared them with LL and ESR of mannose and sucrose (Azorin ef al., 1986). A LL dosimetry system to measure high radiation doses based on tris has also been reported (Azorin and Gutierrez, 1991). This paper presents a study of the dosimetric characteristics of tris obtained by means of ESR and LL techniques, and compares them with those of mannose.
EXPERIMENTAL
Samples (100 mg) of tris, (HOCH&CNH, (Sigma), and D,+,mannose (Merck), were irradiated under electronic equilibrium conditions in a Gammacell 200 @‘Counit at a dose rate of 2 kGy h-‘. ESR spectral measurements were carried out with a Varian X-band ESR spectrometer, employing 9 GHz phase sensitive detection at a constant microwave power level (20 dB) and at room temperature. Weighed amounts of gamma-irradiated tris and mannose (particle size 180-250 pm) in quartz sample tubes were placed in the ESR cavity. The spectra were obtained by scanning the magnetic field and registering them on an x-y recorder. Lyoluminescence readings were made in a thermoluminescence (TL) analyzer, modified to be used as LL reader, which was described earlier (Azorln et al., 1989). A solution 7x10“ mol ml“ of luminol in distilled water was used as the solvent. In each run, aliquots of 10 mg of irradiated sample were dissolved in 5&0.5 ml of solution injected during 10 s. Integration of emitted light photons was continued for 15 s so as to match with the optimum emission of the short-lived component of the LL decay curve after complete dissolution. Single crystals of tris were grown by slow evaporation of saturated aqueous solutions in order to identify the free radical species produced by irradiation of tris. 341
ESR dosimetry and applications
342
The crystals were irradiated at room temperature at an absorbed dose of 30 kGy and the ESR measurements made at room temperature.
RESULTS AND DISCUSSION Figure 1 shows the ESR spectra of gamma-irradiated tris and mannose. Each signal consists of several peaks due to the hyperfine interactions of unpaired electrons with the N and H atoms.
IA 315
Fig. 1. Firstderivative scale is in mT.
320
325
315
320
325
ESR spectrum of tris and mannose irradiated with “Co gamma radiation.
The
For the tris and mannose spectra, the areas (obtained from the double integral of the ESR spectrum) were plotted as a function of dose and compared with the LL response (Fig. 2). The ESR response of tris and mannose are fit to straight lines in logarithmic scale in the ranges from 5 to 10’ Gy for both. Saturation was reached at 3 x 104 Gy. The minimum measurable ESR dose for tris and mannose were 50 and 200 mGy, respectively. No ESR signal fading was observed up to 60 days storage at room temperature. The LL output of tris increases linearly from 5 to 107Gy, saturates, then slowly decreases (Fig. 2a). For mannose, the LL output increases linearly over the range from 3 to ICYGy, as was reported earlier (Azorfn et al., 1989). The LL threshold detection of gamma radiation for tris and mannose are 100 mGy and 500 mGy respectively. No fading was detected in tris and mannose for a period of 6 months after irradiation, when stored at room temperature.
100
’ .
40'
10' Ilose
Fig. 2. ESR and LL responses with gCo gamma radiation.
103
104
10'
‘*11’,’
a ’ lllm’
lo2
’
m“‘ti
103
Dose (GY 1 as a function of dose for: (a) tris and (b) marmose irradiated
104
343
ESR dosimetry and applications
ESR spectra of single-crystals of tris immediately after irradiation indicated the presence of more than one radical species signified by several overlapping lines along equivalent directions. Correlation of evaluated absorbed dose by means of ESR and LL measurements on simultaneously irradiated samples of tris and mannose revealed dose agreement within 5% in the ranges from 20 to 3x10* Gy, and from 50 to 10’ Gy for tris and mannose, respectively. Table 1 summarizes the ESR and LL characteristics of tris compared with dose of mannose.
Table 1. ESR and lyoluminescence characteristics of tris and mannose.
Characteristic ESR dose range (Gy) LL dose range (Gy) ESR detection threshold (mGy) LL detection threshold (mGy) ESR-fading (6 months) LL-fading (6 months)
I
I I I I
tris
mannose
s- 104
5 - 104
s- 103
50 100 nil nil
I
I I I I
3 - 103 200 500
nil nil
In summary, ESR measurements with tris allow determination of absorbed doses in the range of 5 to 104 Gy with an uncertainty of 3%. LL dose measurements in the range of 5 to 1oZGy can be determined with the same uncertainty. Correlation of dose measurements by means of ESR and LL using tris showed agreement within 5%. Thus, tris can be applied to both ESR and LL dosimetry.
REFERENCES Azorfn J., Gutierrez A. and Guadarrama L. (1986) Lyoluminescence of tris (hydroxymethyl) aminomethane in gamma dosimetry. Radiat. Prof. Dosim. 17, 423. Azorln J., Gutierrez A., Mufioz E. and Gleason R. (1989) Correlation of ESR with lyoluminescence dosimetry using some sugars. Appl. Radiat. Isot. 40, 87 1. Azorln J., Gutierrez A. (1991) Development of a lyoluminescence dosimetry system to measure high radiation doses. Proc. Int. Symp. on High Dose Dosimetryfor RadiationProcessing IAEA-SM-3 14 pp. 65-71. Bartlett D.T. and Brown J.K. (1979) Irradiation effects in D-mannose as studied by electron spin resonance spectroscopy. Radiat. En 41, 43. Bartlett D.T., Brown J.K. and Durrani S.A. (1982) Lyoluminescence and electron spin resonance measurements on D-mannose: effects of storage and annealing. Radiat. Efl 66, 233. Ettinger K.V. and Puite K.J. (1982) Lyoluminescence Dosimetry Part I. Principles. Appl. Radiat. Isot. 33, 1115. Puite K.J. and Ettinger K.V. (1982) Lyoluminescence Dosimetry Part II. State-of-the-Art. Appl. Radiat. Isot. 33, 1139.